Air heater



July 30, 1929. J, H, ROHRER 1,722,826

AIR'HEATER n Filed Deo. 12, 1925 6 Sheets-Sheet '3 y July 30, 1929. J. H. RQHRER A 1,722,826

AIR HEATER I i .Filed bec, 12, 1925y l e sheets-sheet 4 Eg@ j /NVENTOR WITNESS @y i v July 30, 1929. J. Hl'Ro'l-IRER` AIR HEATER Filed Dec. l2, 1925 /NVENTR Y n E M fn o 0 T E m. M 2 .w w

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Patented July 30, 1929.

UNITED' STATES JOSIAH H. ROHREB, 0F PIHILADELRHIA., PENNSYLVANIA.

Ain HEATER.

Application mea December Economy in the combustion of fuel is the aim of all designers of boilers and heaters for commercial purposes. Eiiiciency in boiler constructionis attained by the utilization of as much of the heat generated by the combustion of fuel as it ispossible to use. All the heat contained in the products of combustion, when discharged inthe atmos phere, is lost. It is one object of my invention to provide a device by the operation of 'which the heat in the products of combustion, as delivered from the boiler, after passing through any economizer section or arts of the boiler and about to be delivere or discharged into the atmosphere, is, in part, transferred to a' moving column of air, moving counter thereto, the air so heated being made available for various uses, as for instance, delivery to the combustion chamber of the boiler or to driers or to anyr other part of the factory or plant where heated air is used.

A further object of my invention is to provide a construction of air heater in which there is no banking of heat in any particular part et the heater but in which the transfer of heat from the hot gases to the air being heated is continuous throughout the passage ci the gas and the air through the air heater.

A further object of my invention is to so arrange and dispose the parts of thevheater that the temperature of the products of combustion at the time of their exit from the air heater to the atmosphere is lower than the temperature of the air discharged fromthe air heater, thereby making the transference of heat from the gases to the air continuous throughout the entire passage of the hot gases and air through the heater.

A further object of my invention is to provide a construction in which relatively thin layers of air are caused to freely How throughout their travel through the heater between closely arranged banks of tubes through which the heated gases of combustion pass so that the air being heated is not substantially drawn transverse to the tubes but travels longitudinally of the tubes throughout substantially the entire length of the heated tubes.

A further object of my invention is to provide relatively large chambers at or near the ends of the banks of tubes, into which chambers the air being 'heated is discharged so that the air, being heated, may freely discharge therein from lbetween the tubes 12, 1925'. Serial N0. 75,033.

houg'hout the entire width of the bank of u es.4

Further objects of my invention will appear in the specification and claims below.

Referring now to the drawings in which the same reference characters are used to designate. the same parts,

Fig. 1 is a side elevational view, partly in section, of the gasoutlet end or side of the apparatus.

Fig. 2 is a side elevational inlet lside of the apparatus.

Fig. 3 is' a vertical longitudinal section taken on the line 3-3 of Fig. l.

Fig. 4 is a vertical longitudinal section taken on the line 4 4 of Fig. 1.

Fig. 5 is a horizontal sectional view taken on the line 5-5 of Fig. 1.

Fig. 6 is a transverse horizontal sectional View taken on the line 6-6 of Fig. 1.

Fig. 7 is a. somewhat diagrammatic side elevational view illustrative of the manner in which the air heater is utilized.

My improved air heater preferably consists of a closure comprisingva rectangular casing or housing lof boiler plate or similar sheet metal supported on any suitable 'frame work 21 of structural iron or steel held elevated somewhat above the level of the cement or brick iioor 3 by walls of brick or cement 4, one of which may be provided with view of the gas va door or closure 5, to form a chamber Y below the casing or housing 1 for the collection of lsoot and similar solid products of combustion whichl may accumulate therein by reason of the operation of the device and which may be removed therefrom from time to time through the door or opening 5.

The top wall 6 of the casing or housing 1s imperforate. Spaced from the top wall 6 is a horizontal wall or partition 7 provided with a plurality of sets or groups a, b, c, d, e, f, of punched holes into which are eX- panded or otherwise fitted, the upper ends of 100 groups or banks A, B, C, D, E, F, of straight boiler tubes 8, the lower ends ofwhich pass through and are similarly securedV in slmilar groups or sets of holes, a', b', c', d', e', f 1n the bottom tube plate 9 of the casing or h0us-, 105

ing 1.

The space between the upper or top wall 6 and the intermediate wall or tube plate 7 1s divided by a vertical transverse partition'lO to form a. gas inlet chamber X into which 110 the products' of combustion from a boiler or heaterare conducted by an inlet plpe 11 and a gas outlet chamber Z from which the cooled gases of combustion are conducted bya suit' able pipe 12 to the atmosphere. -,The iow of the products of combustion to, through and out of the heater may be effected by a suitable suction fan. Thus, the products of combustion will be drawn through the gas inlet pipe 11 into theV chamber 8 of the banks of tubes. A, B, C to the chamber Y formed by the bottomplate 9, the walls 4 and-the flooring 3, and

thence will pass upwardly through 'the tubes 8 of the banks of tubes'D, E, F t'o the gas outlet chamber Zirom which theconducted away through the cooledl gases are gas outlet pi e ,12. Between lthe `banks of tubes A, B, and the banks of tubes D, E, F, is a vertical dividing partition 13 ofsheet iron extending from the under side ofthe top wall 6 downwardly but the loweredge ofsaid l30.--31 opening into the spaces partition 13 does not reach to the bottom wall or plate 9. It is spaced from thelbottomwallor plate 9 to vpermit the vair partially heated' and consequently. of greater volume than it was when introduced through the ...pipe to pass freely-between the lower end of the plate or partition 113 and the bottom wall 9 of the housing. It vmay be well to statehere thatthe air to be heated -is conducted to my -improved air'heater through a substantially rectangularopening 14 throughthe rearend wall 16 immediately below the hor- -izontal intermediate wall or tubeplate 7l and vertical slots preferably provided with between banks D, E and E, F,A respe ctively. The lower end of .that part of the vertical'partition 13 which is between the .banks A and D, B and F is preferably spaced from the bottom plate or wall 9a distance a little greater. than of tubes D, E,

the `vertical height-of theopening 14 to allow for the expansion of the air' being heatedl and lto lprovide a free passage throughfwhich it may pass without increasing its velocity.

- On each side of the bank of tubes E'and relatively close thereto and extending -from the rear end wall 16 to the intermediate partition 13-are'vertical partitions 17 vand 18, the top edges' of which are substantiallyon the level with the lower horizontal wall ofl the opening 14 and 'the'lower-ends of whichy are substantially on the level with the lower end ofthe vertical par ition 13. `.Like and parallel partitions 19 nd 20 enclose the banks D and F respectively from a point on the 'level with the lower side of the rectangular opening 14 to a point on the'level with the lower end of the intermediate wall or vertical partition 13 so that each of the three banks F is enclosed on four sides for the greater portion of their length, the bank v D by the side wall 21, the partitions 13 and 19 and the rear wall 16; the bank E by the partitions 17, 13 and 18 and the rear wall 16;

X and will be .-drawnI or will pass downwardly through the tubes- :of the lower edge of 22,1rear wall-16 and."partition20'." The up- .perv fand lower Aends of 'the said tubes, however, are -not below the ,partitions..

. Similarly, the bank soenclosed buteXtend above andl f 7o of tubes B on theother andthe 'bank thepartition 13, side wall side of the vertical partition 13 are enclosedl between two vertical partitions 23 and 24,

`the partition tops of said-partit1ons23 and 24 beinga lit- 13-and `the front wall 125, the l tle-below the level of. the tops ofthe parttions 17 and 18 and the lower edges lof said partitions being substa'ntially on the ylevel the vertical partition-13.- Similar vertical partitions 26 and'27' are ad-4 jacent the'bank's A and C of 'tubesthe tops and bottoms off-saidpartions 26-and27 being in the same plane asthe tops and lower edges of -the partitions' 23 and 241v respectively. The bank of tubes A'is enclosed for the greater y*portion of its length bythe partitions 264and 13,- side wall. 21, and. lfront wall 25; and the bankCis similarly encloesd bythe partitions l 27 and 13, sidewall 22, andfront wall 25, In

this way the threebanks of tubes A, B, C are enclosed or encased for the greater portions of their entire lengths by casings lformed by the r,verticalpartition 13, the'sidewalls .21

vand' 22 of' the main casing 1, the. ro'nt'wallv 2 5 and the vertical partitions 23, 2 4, 26and 27.

from the rear-wall 16 to-the front', wall 25,',

and between the partitions 19-17 and 2,6-23,I

Extending"longitudinally ofthe casing'l. between the banks A-V-D, B-fE and. between 4 the banks B'-E and C-F respectively, and

respectively, are longitudinal` partitions '28 and 29 sloping downwardly from the point where they intersectthe dividing partition 13 tothe point where they. engage and are connected to .thejrear and frontwa'lls`16 and 1 The partition 13 is notched from itsl'ower end upwardly tothe pointsov 25- respectively.

its intersection with the partitions 28 and Only between the banksfof'tubes Aand E and the banks B and E and thebank's U and F does the partition'13 extend below the partitions '.28 and 29 as clearly'shown'inFigs. 3. and-4; u

These partitions 28 and 29,-coactingwithv the walls or partitions 17, 18,19, 20, 23,24, y

26 and 274 and. with the partition413 and with the .front wall 25 and the. rear wall-16 and chambers G, H, I, .l above thepartitions 28 and 29 and below the tops of thepartitions with the horizontal tube 'plates` 7,- form 17,.1'8, 19, 20, 2 3, 24, 26 and 27, namely, the 1 chamberv between the-banks D and E; the

chamber H between the banks E and Fg. the *1.126 Y.

above relatively large 'chambers K and L `extend ing the length of the interiorof the casing as clearly shown in Figs. 1 and 4.

In the rear wall of the housing or casing 1 the two vertically disposed rectangular openings 30 and 31 extending from the lower edges of the air inlet opening 14 to the rearA ends of the partitions 28 and 29 respectively, said openings 30 and 31 are respectively in vregistration or alinement with the air inlet chambers G and H. These openings 30 and 31 are for the purpose of facilitating the ingress of air to the chambers G and H whence the air may freely pass around the upper ends of all the tubes to the space between the tubes of the banks of tubes.

The front end wall 25 is provided with similar vertically extending slots or open-A ings 34 and 35, similarly communicating with the air exitchambers I and J between the banks of tubes A--B and B--C. These openings 34 and 35 are enlargementsxof the air exit opening 36 and extend downwardly from the lower edge of the air exit opening 36 to the front ends of the partitions 28 and 29. These openings 34 and 35 are preferably closed by hoods or conduits 37 and 38 formingbranehes of the air exhaust conduit 39 and also serve to formenlargements of the chambers I and J 4into which the air coming vfrom between the banks of tubes A, B and C .freely Hows and circulates.

In Fig. 7 is illustrated, more or less diagrammatically, the manner in which my improved air heater may be operated.

The gas inlet pipe 1 1 is attached to the boiler 40 above and to the rear of the econo- .mizer 41, at the point where the products of combustion are usually discharged to the stack, and to the gas outlet pipe 12 of the heater is attached a fan or blower 42 which, when operated, draws the products of combustion from the boiler 40 through the pipe or conduit 11, through the heater, outlet pipe 12, fan 42 to conduit 43 which may lead toa stack or directly-to the atmosphere.v

The air outlet conduit 39 is attached to a fan or blower 44, operative to draw'air into the heater 1 by air inlet opening 14, thence throughthe heater to the pipe 39 and from the fan a pipe or conduit 45 may run to a point below the grate 46 of the 'boiler 40 to supply hot air to the fuel bein consumed..

A branch pipe or conduit 4 may connect other apparatus requiring hot Iair.

The operation of my air heater is as follows: The Iproducts of combustion, (smoke and hot gases) ,as they leave a boiler 40 and as they are ordinarily discharged to the atmosphere, lare drawn by a suitablel suction4 fan 42 or an equivalent device through the c' hot gas inlet pipe 11 into the gas inlet chamber X whence they pass downwardly through the tubes of the banks A, B, C into the chamber Y below the bottom tube plate 9 and here they sweep downwardly and rearwardly to the lower ends of the pipes 8 of the banks D, E and F, where they pass upwardly through the pipes tol the gas outlet chamber Z from which they are conducted bythe pipe12 to the pump or suction fan 42, whence they are discharged through conduit 43 to the stack or directly to the atmosphere.

The air to be heated may be similarly drawn by a suction fan, pump or draft appliance 44 in through the air inlet opening 14 into the space around the upper ends of the tubes 8 of the banks D, E and F. It fills the chambers G, I-I and circulates therein.

freely sothat from the air inlet chambers G, H, the air iiows over the top edges of the partitions 17, 18, 19 and 20vinto the spaces between thr pipes 8 of the banks of pipes D, E, F. In this way the air is given an opportunity to freely enter the narrow spaces between t-he pipes directly from'the airl inlet chambers G, H and to travel downwardly lengthwise of the pipes 8, on the outside of them, for substantially the full length of the pipes 8. The air flows freely from between the pipes 8 into relatively large chambers K, L which greatly augment the passage between the front and back banks below the partition 13, so that the air being heat/ed enters these chambers from all the spaces between the tubesof banks D, E, F. From these chambers K, L it is again gently drawn downwardly and in between the narrow spaces between the tubes 8 ofthe banks of tubes A, B, C where it is caused to travel upwardly over the tubes 8 for substantially the full length of the tubes 8. Over the tops of the partitions 23, 24, 26 and 27 the air readily passes into and fills the air exit chambers I, J above the partitions 28 and 29 from which and from between the upper ends of the pipes 8 it is conducted through the air exhaust pipe 39 and its hoods 37, 38 by the fan 44 and conduit 45 to a suitable point below the grate 46 where it is discharged. Or a part 7 of the heated air may be conducted by pipe 47 to some other place in the plant where hot air is needed. By virtue of this arrangement the length of the tubes in the banks D, E, and F,

and then thus therefrom into a relatively large chamber around the lower ends of the tubes of the banks D, E, andF. From this last-mentioned chamber the air is drawn up.

wardly between the tubes of the banks A, B

`and C and is discharged at the upper end thereof into a substantially large chamber surrounding the upper ends of the tubes'jof banks A, B and C. y In this way every part of the air being which my improved heated is caused to travel substantially the entire length of the outside of the pipes 8 of the banks A, B; C, D, E, F of hot tubes, through narrow spaces between the tubes, and without very much transverse movement with respect to the pipes. Every part of air is brought into close relationship with the heated pipes and is caused to travel first downwardly and then upwardly a 'distance substantially equal to twice the length of a single tube 8. Itis very essential that the tubes of the banks of tubes should be closely arranged with respect to each other so that the air p/assing between the pipes is substantially in thin layers which are more readily heated than are thick layers of air. l

As a practical illustration of the way in air heater is operated, may take the products of combustion (hot gases and smoke) at say 425 F., and reduce the temperature of such products of com bustion down to 140o F. In so doing I am able to raise the temperature of the air entering the heater at a temperature of say 7Q up to a temperature of 150. When the air so heated is delivered to the fire-box or com bustion chamber of the boilerlvor heater 40 the heat that would have otherwisebeen lost is returned to th-e boiler with a consequent increase Ain the efliciency of the operation of the boiler. All or a part of the air may be taken to a drying room or other place where hot air is required and there utilized, thereby effecting a saving of the cost of heating the air for such uses in an' other manner. In so doing it will be note that at any point in the air heater the' tem erature of the gas in `the tube at that point 1s substantially higher than that outside of the tube at that point. Throughout the apparatus the gases are practically meeting a counterflow of air being heated and the air is practically meeting a counterflow of hot gases. At any oint in the heater there is aA substantial difference between the temperature ofthe air and that of the gases. The gases are always hotter than the air at any given point and the air is always cooler than the gases at any given poin This insures a continual transfer of heat from the hot gases tothe air throughout their passage through the heater so long as the temperature ofthe gas leaving the heater is higher than the, temperature of the air entering the heater.' y i The construction and the operation of an apparatus embodying my invention has thus been describedabove, but itis to be `understood that the details of construction .might and naturally would be 'changed or, altered 'to adapt the heater to different boilers or heaters operating under different conditions and where the air to be heated is required to be raised to different temperatures, but infs rsuch constructidns, the air to be heated will' be yconducted as a counterow over and between tubes through which the products of combustion are being conveyed in the opposite direction and in themanner above described, each particle of air will be brought into close association with the heated products and will be caused to travel substantially the entire length of the tubing through vwhich the products of combustion are being conducted.

Having thus described my invention', whatl 75 I claim and desire to protect by Letters Patent of the United States, is.:

1. An air heater comprising a gas inlet chamber, a gas outlet chamber, an int/ermediate gas chamber spaced from said gas inlet and gas outlet chambers, two spaced banks ofV tubes connect-ing said gas inlet chamber with said intermediate gas chamber, two `spaced banks of tubes connecting said intermediate gas chamber with said gas outlet chamber, partitions within said cas-t ing and forming with said casin an air inlet chamber adjacent said gas out et chamber, forming an air outlet chamber adjacent said gas inlet chamber and formin termediate air chamber between sai air ind let and air outlet chambers on the one thand and said intermediate gas chamber on the other hand, said air inlet chamber being between said two banks of tubes which are connected with said gas outlet chamber and communicating with the spaces between said tubes at the ends thereof which are connected to said gas outlet chamber; said air outlet chamber being between said two banks of tubes which area'connected with said gas inlet chamber and communicating with the spaces between said tubes at the ends thereof which are connected to said gas inlet chamber; and said intermediateair chamber being in communication with the spaces between all of said banks of tubes at the ends thereof which are connected to said intermediate gas chamber.

, 2. An air heater comprising a ing therein a' gas inlet chamber, a gas outlet chamber and an intermediate gas chamber,

a plurality of spaced banks of closely parallel ltubes connecting said gas inlet chamber withv said intermediate gas chamber, rality of spacedl banks of closely disposed parallel tubes connecting vsaid intermediate.,

gas chamber with sa1d gas outlet chamber, an air inlet chamber between said banks of tubes and adjacent said gas outlet chamber,

an air outlet chamber between said banks of tubes and adjacent said gas inlet chamber, and relatively large intermediate air chamber, partitions in said casing parallel to said tubes and `forming with the casing closures surrounding each bank of tubes for the major portion of thelength of said tubes, said dividing said gas inlet vfrom said partltions gas outlet chamber and said air inlet chamber from said air outlet chamber and alon- `130 an in- 90 closure hav- 110 a pluus gas outlet chamber with' said intermediate gas chamber, and thence into said intermediate air chamber, and thence substantially over the entire length of the outer surface of the tubes connecting said .gas inlet chamber with said intermediate gas chamber and thence into said air'outletchamber whereby the air travels relatively rapidly over substantially the entire length of the outer surface of saidtubes in a direction counter to that o f the gases of combustion -passing through said tubes and relatively slowly throu h said intermediate air chamber.

3. n air heater comprising a `closure having a as inlet chamber therein adjacent a side oi said closure, an intermediate gas chamber extending substantially the entire length of said closure adjacent the opposite side of said closure. .a gas outlet chamber adjacent said irst mentioned side of said closure, the combined length of said gas inlet and of said gas outlet chambers being yto-y gether substantially the length ofthe closure, a group'of spaced banks of closely arranged parallel tubes connected at one end with said gas inlet chamber Aand at their other ends with said intermediate gas chamber, a second group of spaced banks of closely arranged parallel tubes connected at one end with said intermediate gas chamber and at their other ends with said gas outletv chamber, a divid- -inggpartition between said groups of spaced banks; of tubes, partitions parallel toI said tubes and between said banks and cooperatin withthe walls of saidl closure and with sai dividing artition to surround the greater portion o the length of said tubes of each bank, said tubes extending beyond `the ends- 4of said parallel partitions, said closure being also provided lwith a longitudinal partition extending the full length of said closure and located between said banks, intermediate the ends of said parallel partitions surrounding said banks and forming an airinlet chamber between said longitudinal. partition and said gas outlet chamber communicating with the spaces between the. tubes at the ends thereof which are connected to, the gas outlet lchamber; forming a relatively large intermediate air chamber between said longitudinal partition and said intermediate gas chamber, .in ffree communication with the spaces between all of said tubes at the ends thereof which are .chamber extending substantially the length of said closure adjacent the bottom side of said closure, a gas outlet chamber adjacent the top side of said closure, the combined length of said gas inlet and outlet chambers being substantially the length of said closure, a group of spaced banks of closely arranged parallel tubes connected at their upper endswith said gas inlet chamber and at their lower ends with said intermediate gas chamber, a second group of banks of closely arranged conl parallel vertical tubes connected at their A l l lowerends with said intermedia-te gas chamber and at their upper ends with said gas outlet chamber, a vertical dividing partition between said groups 'of banks, partitions parali lel to said tubes between said banks and ,cooperating with the walls of said closure and with said vertical dividing partitionto surround the greater portion of theilen'gths of ythe tubes of each bank, said tubes extendin "above and below said parallel partitions, sai' s closureybeing also provided with a longitudinal partition extendin for the full length of said closure and locate between said banks intermediate the ends of said parallel parti'- tions surrounding said tubessaid longitudi rial partition lco-'operating with said vertical dividing partition to form an air inlet chamber below said gas outlet chambercommunieating with the s aces between the upper ends ofthe tubes whic are connected with said gas outlet chamber; said longitudinal partition forming a relativelyl large intermediate air chamber fbetween said longitudinal partition and said intermediate gas chamberin c ommunication with-thespace between all of the tubes at the lower 'ends/thereof; said longitudinal partition forming, with said vertical partition an air'outlet chamber below saidl gas 'inlet chamber and communicatin with thej space between the upper ends o the tubes `Erhich are connected with 'said gas inlet cham- In witness whereofI have hereunto set my hand this'fourthA day of'December, 1925. e ,JosIAH j aolalrnna.- 

